Iceland Shelf large marine ecosystem

Source: NOAA


caption Location of the Iceland Shelf Large Marine Ecosystem. (Source: NOAA)

The Iceland Shelf Large Marine Ecosystem (LME) surrounds the island-nation of Iceland in the Northeast Atlantic Ocean. It is characterized by a subarctic climate and an extreme environment. In this extremely active geological region, the divergence of two plates causes the formation of oceanic crust and the crest of the mid-Atlantic ridge. The LME has a seasonal ice cover and shows marked fluctuations in salinity and temperature. Climate is the primary force driving the LME, with intensive fishing as the secondary driving force. Temperature, currents, tides and seasonal oscillations affect productivity in this LME.


Iceland has a wide volcanic margin marked by broad valleys and a sharply defined slope. Three ocean currents (the East Icelandic Current, the Coastal Current and the Irminger Current) move in a clockwise gyre around the island. A complex system of transverse rides is oceanographically important because it separates the relatively warm and saline waters of the Atlantic from the cold, fresh Arctic waters of the Iceland Sea and Norwegian Sea to the North and Northeast. The Iceland Shelf Large Marine Ecosystem is considered a Class II, moderately high (150-300 grams of Carbon per square meter per year) productivity ecosystem based on SeaWiFS global primary productivity estimates. Extensive primary productivity measurements have been carried out annually in the waters around Iceland for more than four decades. There are marked changes in the spring development of phytoplankton from one year to another. Studies on zooplankton biomass and species composition have been carried out on standard transects during late May-June in Icelandic waters. The highest biomass is found in the front area between the coastal and the Atlantic water off Iceland’s south coast and in the Arctic waters of the East Icelandic current off the northeast coast. Changes in hydrography are impacting the food chain to influence primary production, zooplankton, and the capelin and cod stocks.

Fish and Fisheries

caption Iceland Shelf LME-1. (Source: NOAA)

Fluctuations in salinity, temperature and phytoplankton are factors that contribute to variations of annual catches of cod and small pelagics. Changes in the technology of fisheries has also impacted the total catch. The FAO 10-year trend shows fluctuations in the total catch, from 1.6 million tons in 1990, to 1 million tons in 1991, to 1.6 million tons in 1992, to 1.8 million tons in 1997, and down to 1.3 million tons in 1999. The most important species group in terms of shelf catches are pelagic fishes, representing 51% of the total catch, and cods, hakes and haddocks, representing 25% of the catch. The average yearly catch is 1.3 million tons. There was a peak catch of capelin in 1992-1993. Total catches of the gadiform group have been rather stable during these 10 years. Cod and capelin are two key exploited species in the Icelandic LME and are linked through a tight predator-prey relationship. Other commercial species are saithe, haddock, Greenland halibut, plaice, lemon sole, witch, halibut, dab and herring. The herring catch peaked at about 600,000 tons just before collapsing in the late 1960s. A very important fishery for deepwater shrimp has also developed. At the turn of the century, the fishing industry gradually became more mechanized which led to a catch increase. Intensive fishing is a secondary force driving this LME. The University of British Columbia Fisheries Center has detailed fish catch statistics on this LME. A graphical representation of the data is available below.

Pollution and Ecosystem Health

caption (Source: Manfred Glauser, NOAA)

Climate is the primary driving force within this LME. The simplicity of the main trophic links and the oscillations between warm and cold climatic regimes have dramatic influences on fish yield in this ecosystem. Fluctuations in temperature and salinity can be related to large-scale changes in the atmospheric circulation over the North Atlantic Ocean. Near shore, hydrographic conditions may vary considerably from year to year mainly due to timing and variations of fresh water runoff. Marine pollution appears to be negligible in the fishing grounds of the Iceland Shelf LME. Iceland has 8 pieces of legislation for marine conservation and is about to establish its first major marine conservation area.


caption Source: Manfred Glauser, NOAA)

Early Icelandic settlers were livestock farmers, but by the end of the 19th century, fishing became a major impetus for economic growth. It gradually became Iceland’s main industry. The fishing industry started off with rowboats, but gradually became more mechanized. Foreign fleets, specifically British, began fishing these waters at the end of the 19th century, arriving in large, steam-powered trawlers. There was intense competition with the local fleets. Iceland is one of the few nations in the world today that has been able to build a modern society upon the exploitation of the resources of its surrounding waters. Seafood products constitute about 70-80% of Iceland’s exports. Iceland’s population is quite low (250,000). Iceland’s unique landscapes and hot springs are giving rise to a tourism economy.


Iceland has played a pioneering role in terms of law of the sea. The competition of foreign fishing fleets prompted Iceland to protect its fisheries by extending its territorial limits. The territorial sea was 3 miles in 1901, and was extended to 4 miles in 1952. These extensions were early and bold moves for the time. In 1958, the territorial sea was extended to 12 miles, then in 1972, to 50 miles. British protests against these extensions took the form of 3 “cod wars” (in 1961, 1972 and 1975). In an arbitration opposing Iceland and Great Britain, the International Court of Justice ruled in favor of Iceland. Finally, in 1975, Iceland extended its limits to 200 miles. The Minister of Foreign Affairs has a website that discusses Iceland's territorial sea, economic zone and continental shelf. Iceland has at least 8 pieces of legislation for marine conservation and is about to establish its first major marine conservation area. Iceland works closely with ICES, the International Council for Exploration of the Seas, to monitor the size of fish stocks. There are various restrictions on fisheries (number of days at sea, 1984 quotas on species per vessel per season, the 1995 system to restrict the total cod catch to a maximum of 25% of the estimated stock). The management of Icelandic capelin has been approached in a multi-species context since 1980. The immature stock is specifically protected from fishing. The needs of cod, the main predator, are taken into account prior to the final decision on total allowable catch. Steps have been taken to obtain a better understanding of multi-species interactions in this LME.


Articles and LME Volumes

  • Astthorsoon, O.S. and H. Vilhjalmsson, 2002. Iceland Shelf LME: Decadal assessment and resource sustainability. 2001. In K. Sherman and H.R. Skjoldal, eds. Large Marine Ecosystems of the North Atlantic—Changing states and Sustainability. Elseviers. 219-243. ISBN: 0444510117.
  • FAO, 2003. Trends in oceanic captures and clustering of large marine ecosystems—2 studies based on the FAO capture database. FAO fisheries technical paper 435. 71 pages. FAO Fisheries & Aquaculture-Large Marine Ecosystems.
  • Prescott, J.R.V. 1989. The political division of large marine ecosystems in the Atlantic Ocean and some associated seas. In K. Sherman and L.M. Alexander, eds. Biomass Yields and Geography of Large Marine Ecosystems. AAAS Selected Symposium 111. Westview Press, Boulder CO. 395-442. ISBN: 0813378443.

Other References

  • Anon., 1997. Fjolstofnarannsoknir 1992-1995 (Muutli-species investigations 1992-1995. In Icelandic. Hafrannsoknastofnunin Fjolrit, 57, 411 p.
  • Dickson, R.R., J. Meinke, H.H. Lamb, S.A. Malmberg and A.J. Lee, 1988. The “Great Salinity Anomaly” in the Northern North Atlantic 1968-1982. Progress in Oceanography, 20:103-151.
  • Gudmundsson, K. 1998. Long-term variation in phytoplankton productivity during spring in Icelandic waters. ICES journal of marine science, 55:635-643.
  • Jakobsson, J. and G. Stefansson, 1998. Rational harvesting of the cod-capelin-shrimp complex in the Icelandic marine ecosystem. Fisheries Research, 37:7-21.
  • Jonsson, J., 1994. Fisheries off Iceland 1600-1900. ICES Marine Science Symposia, 198:3-16.
  • Malmberg, S.A., J. Mortensen and H. Valdimarsson, 1999. Decadal scale climate and hydrobiological variations in Icelandic waters in relation to large scale atmospheric conditions in the North Atlantic. ICES CM 1999/L:13. 9 p.
  • Schopka, S.A., 1994. Fluctuation in the cod stock off Iceland during the twentieth century in relation to changes in the fisheries and the environment. ICES Marine Science Symposia, 198:175-193.
  • Skjoldal, H.R., T.T. Noji, J. Giske, J.H. Fosså, J. Blindheim, and S. Sundby. 1993. Mare Cognitum: Science plan for research on marine ecology of the Nordic Seas (Greenland, Norwegian, Iceland Seas) 1993-2000. A regional GLOBEC program with contributions also to WOCE and JGOFS. Institute of Marine Research, Bergen, Norway, 162 p. ISBN: 8274610385.
  • Thordardottir, T., 1984. Primary production north of Iceland in relation to water masses in May-June 1970-1989. ICES CM 1984/L:20, 17 p.

Disclaimer: This article is taken wholly from, or contains information that was originally published by, the National Oceanic and Atmospheric Administration (NOAA). Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the National Oceanic and Atmospheric Administration (NOAA) should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.



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